Sealed polarized relay



2 Sheets-Sheet 1 Filed Nov. 29, 1956 INVENTORQS. HOWARD E. CORBITT R OBERT w. CUNNINGHAM BY RALPH M. HILL Jr SEALED POLARIZED RELAY Filed NOV. 29, 1956 2 Sheets-Sheet 2 INVEN TOR. HOWARD E. CORBITT ROBERT W. CUNNINGHAM RALPH M. HILL JK United States Patent ce SEALED POLARIZED RELAY Howard E. Corbitt and Robert 'W. Cunningham, Monrovia, and Ralph M. Hill, Jr., Azusa, Calif., assignors to Aerojet-General Corporation, Azusa, Califi, a corporation of Ohio Application November 29, 1956, Serial No. 625,061

6 Claims. (Cl. 200-87) This invention relates to electrical switches and more particularly to magnetically-operated switches.

An object of this invention is to provide a switch of this type wherein the switch contacts are protected from liquids or gases which might have a deleterious effect.

The invention is carried out by provision of resilient permeable switch contact elements within an enclosed envelope which is placed in operating relation with magnets in a magnetic circuit.

A feature of the invention resides in means for moving the magnets in relation to the permeable switch elements, in response to a pressure or force which is to actuate the switch.

In a preferred arrangement the magnets are moved along the outside of the envelope containing the switch elements.

The foregoing and other features of the invention will be better understood from the following detailed description and the accompanying drawings, of which:

Fig. l is an enlarged view partly in cross section of a switch according to this invention, shown in its actuated position;

Fig. 1a is a top view of an element used in the switch of Fig. 1;

Fig. lb is an end view of the element of Fig. In;

Fig. 1c is an enlarged top view of fragments of a pair of elements according to Figs. 1a and lb, as used in the switch of Fig. 1;

Fig. 2 is a side view of the switch of Fig. 1, shown true size;

Fig. 3 is an end view of the switch of Fig. l and Fig. 2;

Fig. 4 is a cross-section view taken at line 4-4 of Fig. 1;

Fig. 5 is a crosssection view of a fragment taken at line 55 in Fig. 4;

Fig. 6 is a fragmentary side'view in cross section of parts in Fig. 1 showing the related position of parts when the switch of Fig. l is unactuated; and

Fig. 7 is a schematic wiring diagram for the switch of Figs. 1 to 7.

In Figs. 1 and 2 there is shown an assembled switch having a body 10 which is adapted to be attached within a threaded hole in a chamber subjected to pressure, by means of exterior threads 11 on the body 10. The body is hollow, having an internal area 12 which is concentric around the center line 13 of the assembled switch. A housing 14 fits on one end into the unthreaded end of the body and is welded at 15 to the body 10. The housing 14 has exterior threads 16 on the other end. A connector cap 17 of the same diameter as the threaded end of the housing also has exterior threads 18 of the same size as the housing threads. A connector 19 attaches the connector cap to the housing by means of internal connector threads 20. The connector is provided with a number of connector lugs 21 each having a wire hole 22. The housing 14 also has a wire hole 23. The connector 19 may be tightened down and held in place by a lock wire 24 which goes through the housing wire hole 23 and the vcross section at the left (in Fig. la).

2,923,791 Patented Feb. 2, 1960 nearest lug wire hole 22. The housing 14 has an internal chamber 25 which is concentric around the center line 13 of the assembled switch. The housing end within the body is drilled and countersunk at 26 concentric around the center line 13. A non-magnetic tube 27, which may be of metal, having an open end 28 and a closed end 29 is attached to the housing by inserting the open end 28 into the drilled and countersunk body portion 26 and welding the two together at 30 in the countersunk portion.

Within the tube 27 and the housing chamber 25 there is mounted an electric switch which is enclosed in a sealed insulating tube 31 which may be of glass or the like, and is preferably evacuated of air or gas. The switch is of a type available commercially such as is obtainable from the Revere Corp. of America. The switch has two cantilever electrically contacting elements 32 and 33 shown separately in Figs. 1a and 1b, each sealed through one of the ends of the tube 31. These elements each have a resilient flat portion 33a at the right (in Fig. la) and a substantially rigid mounting portion 34a of semi-circular The portion 34a is part of the element which is sealed through the tube. Flat portion 332 bends easily when it is affected by mag netic forces. The cantilever strips are of high magnetic permeability and low retentivity and each extends from its respective end of the tube to a position just beyond the tube center, so that the free ends of the strips overlap. The strips 32 and 33, as shown in Fig. 10, each have a wide surface of their rectangular cross section directed toward one another so that when they bend at their resilient portions the fiat surfaces directed toward each other will move toward or away from the opposite facing fiat surface of the other strip.

The overlapping ends of the strips located near the tube center are preferably gold plated so that they give good electrical contact with each other even after repeated use. The ends of the cantilever strips sealed through the evacuated tube 31, protrude to some extent outside the tube. The protruding portion of strip 32 within the closed end 29 of the tube 27 is embedded in a shock-absorbing mount 34 of rubber or similar material. The protruding portion of the cantilever strip 33 extends centrally into the housing chamber 25 where it is centrally supported by a similar mount 35. A part of cantilever strip 33 extends beyond the mount 35 and has attached to it a pair of lead wires 36. A similar lead wire 37 extends from the protruding end of cantilever strip 32 along the outside of the glass tube through the housing chamber 25 and connects to a prong 38.

A wiring diagram is shown in Fig. 7 having switch contacts 33 and 32, wiring 36 and 37 and prongs 38 and 39 identified by like numbers as in Fig. 1. Lead wires 36 connect to a pair of prongs 39 which are shown in the end view in Fig. 3 but are not shown in Fig. 1. The prong 38 and the prongs 39 are located in a hollow prong chamber 40. There are three prongs so that connection may be made to a three-prong plug, although a three-prong plug is not essential to the invention. The outside of the connector cap is provided with threads at 41 which may be used if desired to receive an internally threaded cap or the like which may fit over a prong receptacle so that tight electrical contact may be maintained when a connection is made to the prongs. The prongs are attached to a prong base 42 which should be of non-conductive material. Each prong is attached to the base 42 by a cone-shaped portion of the base. A non-conductive prong cap 43 fits over the three cone-shaped portions of the prong base and keeps the prongs positioned from one another. The prong base 42 and prong cap 43 are shaped to fit the internal surfaces of the housing 14 and the connector cap 17 respectively so that the assembly may be tightened. An adhesive 44 fills portions of the housing chamber 25 48 and 49 are shown.

or its equivalent. switch at the prongs 38-and 39.

between the switch mount 35 and the prong base 42 so that the lead wires are insulatedfrom one another.

An assembly of permanent magnets 45 are surrounded be used. The four permanent type magnets 45 are of. 7

similar shape, lie longitudinally in the cylinder 46 and are concentrically located around the assembly-axis 13 with all of their like poles facing in the same direction. The magnet assembly comprises the magnets 45, the moulded cylinder 46, two washers 52 and 53 located on each end of the cylinder 46, an inner washer 54 and a hollow plunger 55. The plunger 55 slides over the closed end 29 of the tube 27. The outer end of the plunger 55 has a contact surface 55:: by which the plunger maybe pushed forward intothe body and around the tube 27.

' The outer end of the plunger is provided with two vent 4" a 32 and33 of high permeability and low retentivity will then have north poles induced in their ends by the concentrically located magnets. The like polarity is induced in the two strips because magnetic lines of flux tend to 1 take the path through the strips which are of a high permeability. With the strip contact ends largely removed from between the concentric magnets the resilient portions of each strip bend away from one another causing the strip contact ends of like polarity to separate since they repel one another. a I

The switch can be operated by mechanical pressure of a piston 61 or float, or the like, in the tank or chamber;

whichmoves in response to the quantity or condition of holes 56 and 57, one of which is shown in Fig. 1 and the 'other is shown in Fig. 2. The plunger inner end, which extends into the body 10, has a flanged base 58 which is of the same diameter as'the washers 52, 53 and 54 and the cylinder 46. The five members 58, 52, 53, 54 and 46, which have the same diameter, are shown adjacent to one :another in Fig. 5. Each'of these parts is provided with aligned tapped holes 48 and 49 and the aligned pair of vent holes47 shown in Fig. 4. The pair of vent holes 47' in the various parts are kept aligned by the screws 5%) and 51 inserted from opposite ends in tapped hole 48, as shown in Fig. 5, andtwosimilar screws which are located in tapped hole 49 but are not here shown in any view.

The four screws in the two tapped holes 48 and 49 not only align the vent holes 47 but they also make a single connected unit of the members 58, 52, 53, 54 and 46" which shall be referred to as the magnet assembly. The magnet assembly is shown in Fig. 4 where the .vent holes 47 through the molding compound and the tapped holes The screws are inserted in the tapped holes to align the vent holes 47 in the various parts of the magnet assembly. w v V 1 z 7 Located to the right of the magnet assembly and adjacent to it, is a coil spring 60 which pushes against the magnet assembly by contact on thewasher 54. A sn'ap ring 59 in a groove 59a, within the hollow area 12 of the between the end of the housing 14 andthe washer 54.

To use the switch, it is threaded 'by threads 11 into the wall of the chamber or tank which is to operate it. Such a chamber, for example, may be a propellant tank for a rocket; although it will be understood that the switch is not limited to such use. If the chamber or tank contain acid, such as is frequently the case in a propellant tank, the metal parts of the switch which are in contact with fluids in the chamber interior may be of an acid-resistant metal and the molded cylinder 46 may be of a nonmetallic acid-resistant compound such as the commercial products Kel-F or Teflon, which are resistant to acid Electrical connection is madeto the In the normal unactuatedswitch position, the magnets are withdrawn to the left from the position around the vicinity of the gold-plated ends of the contacts 32 and 33, as shown in Fig. 6. This is the normal unactuated position in which the magnet assembly plunger 58 is kept "in contact with snap ring 59 by compression spring 66 (see Fig. 1). The righthand end of the magnets are of the same polarity, foreXample north poles, and in the unactuated position of a switch, shown'in Fig. 6, the strips fluid in the chamber. The piston61 contacts the plunger contact surfaces 554: and pushes the plunger 55 and the concentric magnet assembly of which it is a part, longitudinally toward the spring 60'along the tube 27 on all sides of the tube. The plunger flange '58 moves away from the limiting snap ring 59 and the compression spring on the opposite side of the magnet assembly is compressed between the washer 54 and the end ofthe housing 14.

This actuated conditionof the switch is shown in Fig. 1. The righthand ends of the permanent magnets are around the overlapping contact ends of strips 32 and 33 and in this position the magnetic flux paths concentrate themselves in the highly permeable strips; In'Fig. 1,

flux emanates from the righthand poles, for example, the north poles, of the permanent magnets and enters the permanent magnets makesthe attachment end of strip 33a south pole-and passes through the strip 33 to its free end which becomesof north polarity. Thesouth polarity'of the contact end of-strip 32 and the north polarity of the contact end of strip 33rcauses the contact ends to attract one another. The strips 32 and 33 bend toward one another along their resilient portions and'the contact ends of strips 32 and 33jmake electrical contact on their gold-plated ends to close the switch.

Removing mechanical pressure from contact surface 55a again causes the compression spring to expand and return the magnet assembly and therefore the switch contacts to their unactuated position asshown in Fig. 6. The magnet assembly vent holes'47- permit equalizing of pressures on the two sides of the magnetfassembly as the magnet assembly is moved either'to the right or to the left. The magnet assembly movement is then affected only by the piston actuation and the'comp'ression spring andnotin any wayby unbalanced pressures. 1

The vent holes 56 and 57 in the plunger 55 also permit equalizing of pressure inside and outside the slidable plunger as it is moved.

*The switch of the present inventionhas a number of -to its prong receptacle and turning its threaded body out of a chamber when the chamber is empty. Theswitch will not leak under pressure since the switch has internal areas between its parts whichare pressure proof because the switch parts'in correspondence with'the pressure chamber are soldered or welded together. 'Theswitch assembly is rugged and can withstand the mechanical shock of a piston or the like, since the part hit by the piston in 'no 'way causes mechanical shock to the rela- V tively delicate'electrical switch contacts because there is only a magneticenergy linkage between mechanical and electrical parts. The electrical switch contacts are eflec tively sealed against fumes and'liquid'by its own con- I struction and by being sealed in the tube. The parts not,

sealed from fumesand liquid are parts which can con veniently be composed of. materials which are substantially acid resistant, such as the acid resistant molding compound of the magnet assembly cylinder. The shock resistantmounts of the vacuum tube type switch protect the relatively delicate switch contacts from vibration and shock. The switch operates elfectively over a wide temperature range, for example from 65 F. to +160 F.

The concentric arrangement of the permanent magnets provides a strong and uniform concentric field pat tern which concentrates itself in the high permeability cantilever strips of the switch, and produces strong mag netic forces required to operate the switch contacts elfectively with good electrical contact.

We do not desire that our invention be limited to the particular embodiment shown, but only in accordance with the scope of the following claims.

We claim:

1. An electric switch assembly comprising a tubular envelope having a longitudinal axis, switch contacts within said envelope, said switch contacts comprising electrically conducting flexible overlapping reeds of magnetic material adapted to contact each other, a hollow plunger having at least part of the envelope within it, means for sliding said plunger over said envelope in a direction colinear with said longitudinal axis, a plurality of permanent magnets, and means attached to the plunger holding said permanent magnets in spaced positions around the circumference of the envelope, whereby movement of the plunger moves the magnets in relation to the overlapped reeds to operate the switch.

2. An electric switch according to claim 1 in which a spring is arranged in relation to the plunger to urge it in one direction along said axis, and means is provided for moving the plunger against the force of said spring in the opposite direction along said axis.

3. An electric switch according to claim 2 in which the means attached to the plunger holding said permanent magnets comprises molding compound.

4. An electric switch assembly comprising a housing having a cylindrical portion closed at one end and open at its other end, a tubular envelope within said cylindrical portion and co-axial with the longitudinal axis thereof, switch contacts within said envelope, said contacts comprising electrically conducting flexible overlapping reeds of magnetic material adapted to contact each other, a tubular plunger fitted over the end of said envelope adjacent the open end of said housing, an annular means attached to said plunger and fitted between the inner cylindrical wall of said housing and the outer tubular wall of said envelope and slidable between said inner and outer walls in the direction of said longitudinal axis, and magnet means supported by said annular means, whereby movement of the plunger moves said magnet means in relation to the overlapping reeds to operate the switch.

5. An electric switch assembly according to claim 4 in which a compression spring placed between said annular means and the closed end of said housing urges the plunger in the direction away from said closed housing end, and a stop means is fastened to said housing at the opposite side of said annular means from said spring to limit the movement of said plunger.

6. A switch according to claim 4 in which vent means is placed in the end of the plunger remote from the annular means communicating from the atmosphere to the inside of the plunger and vent means is provided through the annular means communicating between the atmosphere and the region within the housing between the annular means and the closed end of the housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,438,897 Brown Apr. 6, 1948 2,487,052 Hastings Nov. 8, 1949 2,600,011 MacDonald et a1. June 10, 1953 2,658,970 Hurley Nov. 10, 1953 FOREIGN PATENTS 658,662 Germany June 29, 1938 669,932 Great Britain Apr. 9, 1952 

